The present invention relates to a new configuration for the dimples on a golf ball surface which improve the flight characteristics of the ball.
According to United States Golf Association (U.S.G.A.) rules, a golf ball may not have a weight in excess of 1.620 ounces or a diameter smaller than 1.680 inches. The initial velocity of balls conforming to U.S.G.A. regulations may not exceed 250 feet per second with a maximum tolerance of 2%. Initial velocity is measured on a standard machine kept by the U.S.G.A. A projection on a wheel rotating at a defined speed hits the test ball, and the length of time it takes the ball to traverse a set distance after impact is measured. U.S.G.A. regulations also require that a ball not travel a distance greater than 280 yards when hit by the U.S.G.A. outdoor driving machine under specified conditions. In addition to this specification, there is a tolerance of plus 4% and a 2% tolerance for test error.
These specifications limit how far a struck golf ball will travel in several ways. Increasing the weight of a golf ball tends to increase the distance it will travel and lower the trajectory. A ball having greater momentum is better able to overcome drag. Reducing the diameter of the ball also has the effect of increasing the distance it will travel when hit. This is believed to occur primarily because a smaller ball has a smaller projected area and, thus, a lower drag when traveling through the air. Increasing initial velocity increases the distance the ball will travel.
Drag on a golf ball is also reduced by forming a plurality of dimples, generally circular, in the outer surface of the ball. The dimples serve to reduce the pressure differential between the front and rear of the ball as it travels through air.
Numerous dimple configurations for use on golf balls are well-known in the patented prior art. The Kempshall U.S. Pat. No. 922,773, for example, discloses a golf ball having circular recesses in the surface thereof, with a central protuberance being arranged within each recess. In one embodiment, an outer band projects from the surface of the ball around each recess. The Kobayashi U.S. Pat. No. 4,787,638 discloses a golf ball having a plurality of first circular dimples formed in the outer shell of the ball and a plurality of secondary dimples arranged within the first dimples. This arrangement produces a turbulent air flow boundary layer at the surface of the ball when it travels at lower air speeds.
While these dimpled golf balls of the prior art differ from the more conventional circular dimpled balls, they have not achieved sufficient results as to attain acceptance in the marketplace. The present invention was developed in order to create a dimpled golf ball with improved flight characteristics which also conforms with U.S.G.A. standards.
Accordingly, it is a primary object of the present invention to provide a golf ball having a spherical surface with a plurality of uniquely configured dimples thereon. Each dimple includes a generally annular portion having an inner configuration and an outer configuration, one of the configurations being non-circular. Each dimple further including an inner portion having an outer configuration corresponding with the inner configuration of the annular portion. At least one of the annular and inner portions extends above the surface of the golf ball.
It is yet another object of the invention to provide a golf ball wherein the dimples comprise at least two groups. The first group of dimples each has an annular portion having a first configuration and the second group of dimples each has an annular portion having a second outer configuration.